/*
 * $Id: PDFOutput.java,v 1.3 2007/09/22 12:48:16 gil1 Exp $ $Date: 2007/09/22
 * 12:48:16 $ This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of the License,
 * or (at your option) any later version. This library is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY; without even the
 * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
 * the GNU Lesser General Public License for more details. You should have
 * received a copy of the GNU Lesser General Public License along with this
 * library; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place, Suite 330, Boston, MA 02111-1307 USA
 */
package gnu.jpdf;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Vector;

/**
 * This class is used to write a PDF document. It acts as a wrapper to a real
 * OutputStream, but is necessary for certain internal PDF structures to be
 * built correctly.
 * 
 * @author Peter T. Mount
 * @author Eric Z. Beard, ericzbeard@hotmail.com
 * @version $Revision: 1.3 $, $Date: 2007/09/22 12:48:16 $
 */
public class PDFOutput
{
    /**
     * This is the actual OutputStream used to write to.
     */
    protected OutputStream os;
    
    /**
     * This is the OutputStream used to write each object to.
     * <p>
     * We use a separate stream, because we need to keep track of how many bytes
     * have been written for each object for the xref table to work correctly.
     */
    protected ByteArrayOutputStream baos;
    
    /**
     * This is the current position within the stream
     */
    protected int offset;
    
    /**
     * This vector contains offsets of each object
     */
    protected Vector<PDFXref> offsets;
    
    /**
     * This is used to track the /Root object (catalog)
     */
    protected PDFObject rootID;
    
    /**
     * This is used to track the /Info object (info)
     */
    protected PDFObject infoID;
    
    /**
     * This creates a PDF OutputStream
     * 
     * @param os
     *            The output stream to write the PDF file to.
     * @throws IOException
     *             if there is an I/O error.
     */
    public PDFOutput(OutputStream os) throws IOException
    {
        this.os = os;
        offset = 0;
        offsets = new Vector<PDFXref>();
        baos = new ByteArrayOutputStream();
        
        // Now write the PDF header
        //
        // Note: As the encoding is fixed here, we use getBytes().
        //
        baos.write("%PDF-1.2\n".getBytes());
        
        // This second comment is advised in the PDF Reference manual
        // page 61
        baos.write("%\342\343\317\323\n".getBytes());
        
        offset = baos.size();
        baos.writeTo(os);
    }
    
    /**
     * This method writes a PDFObject to the stream.
     * 
     * @param ob
     *            PDFObject Obeject to write
     * @exception IOException
     *                on error
     */
    protected void write(PDFObject ob) throws IOException
    {
        // Check the object to see if it's one that is needed in the trailer
        // object
        if (ob instanceof PDFCatalog)
            rootID = ob;
        if (ob instanceof PDFInfo)
            infoID = ob;
        
        offsets.addElement(new PDFXref(ob.getSerialID(), offset));
        baos.reset();
        ob.write(baos);
        offset += baos.size();
        baos.writeTo(os);
    }
    
    /**
     * This closes the Stream, writing the xref table
     */
    protected void close() throws IOException
    {
        // Make sure everything is written
        os.flush();
        
        // we use baos to speed things up a little.
        // Also, offset is preserved, and marks the begining of this block.
        // This is required by PDF at the end of the PDF file.
        baos.reset();
        baos.write("xref\n".getBytes());
        
        // Now a single subsection for object 0
        // baos.write("0 1\n0000000000 65535 f \n".getBytes());
        
        // Now scan through the offsets list. The should be in sequence,
        // but just in case:
        int firstid = 0; // First id in block
        int lastid = -1; // The last id used
        Vector<PDFXref> block = new Vector<PDFXref>(); // xrefs in this block
        
        // We need block 0 to exist
        block.addElement(new PDFXref(0, 0, 65535));
        
        for (PDFXref x : offsets)
        {
            
            if (firstid == -1)
                firstid = x.id;
            
            // check to see if block is in range (-1 means empty)
            if (lastid > -1 && x.id != (lastid + 1))
            {
                // no, so write this block, and reset
                writeblock(firstid, block);
                block.removeAllElements();
                firstid = -1;
            }
            
            // now add to block
            block.addElement(x);
            lastid = x.id;
        }
        
        // now write the last block
        if (firstid > -1)
            writeblock(firstid, block);
        
        // now the trailer object
        baos.write("trailer\n<<\n".getBytes());
        
        // the number of entries (REQUIRED)
        baos.write("/Size ".getBytes());
        baos.write(Integer.toString(offsets.size() + 1).getBytes());
        baos.write("\n".getBytes());
        
        // the /Root catalog indirect reference (REQUIRED)
        if (rootID != null)
        {
            baos.write("/Root ".getBytes());
            baos.write(rootID.toString().getBytes());
            baos.write("\n".getBytes());
        }
        else
            throw new IOException("Root object is not present in document");
        
        // the /Info reference (OPTIONAL)
        if (infoID != null)
        {
            baos.write("/Info ".getBytes());
            baos.write(infoID.toString().getBytes());
            baos.write("\n".getBytes());
        }
        
        // end the trailer object
        baos.write(">>\nstartxref\n".getBytes());
        baos.write(Integer.toString(offset).getBytes());
        baos.write("\n%%EOF\n".getBytes());
        
        // now flush the stream
        baos.writeTo(os);
        os.flush();
    }
    
    /**
     * Writes a block of references to the PDF file
     * 
     * @param firstid
     *            ID of the first reference in this block
     * @param block
     *            Vector containing the references in this block
     * @exception IOException
     *                on write error
     */
    protected void writeblock(int firstid, Vector<PDFXref> block)
            throws IOException
    {
        baos.write(Integer.toString(firstid).getBytes());
        baos.write(" ".getBytes());
        baos.write(Integer.toString(block.size()).getBytes());
        baos.write("\n".getBytes());
        // baos.write("\n0000000000 65535 f\n".getBytes());
        
        for (PDFXref x : block)
        {
            baos.write(x.toString().getBytes());
            baos.write("\n".getBytes());
        }
    }
} // end class PDFOutput
